The main objectives of this work package are;

  • To develop the most potential extraction/fractionation/purification protocol for the recovery of tannins and sugars from softwood barks and lignin and sugars from straw hydrolysis residue.
  • To up-scale the developed processes and produce adequate amounts of each fraction to be delivered to WP3 for application testing.


The project is developing technologies for the recovery of tannin, lignin and cellulose from biomass residues to be used as intermediates for further upgrading. The raw materials that are being studied are abundant and low-value side streams.

Here is some of the work completed so far:

  • On-going studies have identified the most promising industrial source of softwood bark for the recovery of tannin, as well as feasible technologies for the extraction of tannin and lignin from bark.
  • The cellulosic residue has turned out to be promising raw material for saccharification (the process of breaking cellulose into simple sugars) and further biotechnical upgrading - the fermentation to various products that are included in rehap.
  • The hydrolysis residue lignin can be purified to yield lignin for the planned end uses.
  • Both fractionation lines are being up-scaled to produce adequate quantities of intermediated for other WPs.


Recent studies have been focused on the residual generated in the processes of Biochemtex to generate bioethanol (petroleum substitute) from wheat straw or poplar.

Rehap have optimised Biochemtex's second generation (2G) technology to process lignocellulosic biomasses at pilot and demo scale in order to produce the lignin-rich residue and use it as starting material for the recovery of lignin and sugars for further project research. The project alongside Biochemtex found that the combination of separating large amounts of solids from liquids using polyelectrolytes as a separating agent as well as the drying technique, is a good solution to significantly reduce the moisture content (from 60-70% by 7-10%) to allow lignin co-product to be used successfully for combustion and/or chemical valorisation.

The next step is to take this residual and obtain one-part lignin precipitated in acid conditions and also to revalorise the residuals generated in the isolation of the lignin.

The large-scale recovery of the target intermediates is in progress and in the future the industrial partners will get samples for testing in the pilot scale production units.

BBEPP and upscaling

Parallel to this, project research partners are supporting work by lab scale testing and analytical studies.

BBEU at the Bio Base Europe Pilot Plant (BBEPP) is one of the partners working with Rehap to help with the upscaling of the extraction of tannin and lignin from bark and residues. The extraction of tannins was successfully transferred to the BBEPP lab and scaled from lab to pilot scale. The tannin solution was then clarified and has been delivered to Foresa and Rampf for further modification.

Developments in 2,3-butanediol

In parallel to this development with VTT and BBEPP, partners, TECNALIA have been working on the saccharification – the process of breaking down a complex carbohydrate, in this case cellulose, using hydrolysis into its simplest sugars – of the cellulosic residue generated by the purification of lignin from the woody material, poplar.

Promising results from poplar’s second generation sugars have revealed close comparisons to 2,3-BDO production using first generation sugars; sugars found in food crops using standard processing technologies.

In other developments, the fermentability of the sugars obtained from bark in BBEPP at pilot scale, have also been optimised by BIOSYNCAUCHO with excellent results in terms of 2,3-BDO production, yield and productivity.


VTT has developed a method to extract high yields of pure tannins from softwood bark for use as a raw material for producing resins used in wood products and other material applications. The residual fibre fraction can be used to produce sugar for fermentation products.

The work package is close to finishing.

Tecnalia will be attending the VTT conference – 8th Nordic Woods Biorefinery Conference (NWBC) – in Finland and will be presenting a paper, "Polyphenols from softwood bark for phenolic resins", on their recent results including communication for the precipitation of lignin. It covers results both from Rehap and another, nationally funded (Business Finland, former Tekes), project SusBinders that has similar objectives.


Paper – The influence of softwood bark origin on tannin recovery by hot-water extraction

Paper – Alkaline cooking and lignin tannin fractions
Paper – By Tecnalia with contribution from VTT and BBEPP and will include results from the up-scaling processes at BBEPP

Work package leader 

Tarja Tamminen - 

Tarja Tamminen is a Principal Scientist at VTT Research Centre of Finland. She is working in the Biomass processing research area with special focus on biorefinery chemistry. With a PhD in organic chemistry her experience is mainly on traditional end emerging chemical wood processing technologies and valorisation of the side stream components, particularly lignin.